Engine systems and methods of operating an engine

ABSTRACT

One embodiment of the present invention is a unique method for operating an engine. Another embodiment is a unique engine system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for engines and engine systems. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith.

FIELD OF THE INVENTION

The present invention relates to engines, and more particularly enginesthat are supplied with reformed fuel, and methods for operating suchengines.

BACKGROUND

Engine systems that effectively use reformed fuel remain an area ofinterest. Some existing systems have various shortcomings, drawbacks,and disadvantages relative to certain applications. Accordingly, thereremains a need for further contributions in this area of technology.

SUMMARY

One embodiment of the present invention is a unique method for operatingan engine. Another embodiment is a unique engine system. Otherembodiments include apparatuses, systems, devices, hardware, methods,and combinations for engines and engine systems. Further embodiments,forms, features, aspects, benefits, and advantages of the presentapplication will become apparent from the description and figuresprovided herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 schematically illustrates some aspects of a non-limiting exampleof an engine system in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

For purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings, and specific language will be used to describe the same.It will nonetheless be understood that no limitation of the scope of theinvention is intended by the illustration and description of certainembodiments of the invention. In addition, any alterations and/ormodifications of the illustrated and/or described embodiment(s) arecontemplated as being within the scope of the present invention.Further, any other applications of the principles of the invention, asillustrated and/or described herein, as would normally occur to oneskilled in the art to which the invention pertains, are contemplated asbeing within the scope of the present invention.

Referring to FIG. 1, some aspects of a non-limiting example of an enginesystem 10 in accordance with an embodiment of the present invention areschematically illustrated. Engine system 10 is configured for reducedNO_(x) emissions by employing a reformer to generate hydrogen (H₂) aspart of a hydrogen assisted lean operation scheme. Engine system 10includes an engine 12 and a fuel delivery system 14. In one form, engine12 is an internal combustion engine, e.g., a spark-ignition pistonengine. In other embodiments, engine 12 may take other forms, e.g., agas turbine engine, or another type of reciprocating engine. Engine 12includes, among other things, an air intake 16 and a combustion chamber18. In various embodiments, air intake system 16 may be pressurized by acompressor (not shown), e.g., a turbocharger, a supercharger and/or anyother type of compressor. In one form, combustion chamber 18 is apre-combustion chamber positioned upstream of and in fluid communicationwith one or more main combustion chambers, e.g., piston combustionchambers or, e.g., a precombustion zone in or coupled to gas turbineengine combustion chambers. In other embodiments, combustion chamber 18may be or include one or more main combustion chambers, e.g., a mainpiston engine combustion chamber or a main gas turbine engine combustionchamber.

In one form, fuel delivery system 14 is an auxiliary fuel deliverysystem that delivers to engine 12 only a portion of the fuel consumed byengine 12 during engine 12 operations, whereas the balance of fuel issupplied by a main fuel system (not shown). In other embodiments, fueldelivery system 14 may supply most or all of the fuel consumed by engine12 during engine 12 operations. In one form, fuel delivery system 14includes a compressor 20 operative to receive an oxidant from an oxidantsource 22; a fuel flow control valve 24 operative to receive andregulate a flow of fuel from a fuel source 26, a merging chamber 32 anda reformer 34. In one form, oxidant source 22 is air pressurized by anengine 12 compressor (not shown), e.g., a compressor used to pressurizeengine air intake 16. Compressor 20 is configured to increase thepressure of the oxidant to above the pressure at the engine air intake.In other embodiments, oxidant source 22 may be, for example and withoutlimitation, ambient air or oxygen-enriched air or nitrogen enriched air.In one form, fuel source 26 is a source of pressurized fuel, for exampleand without limitation, compressed natural gas (CNG). In otherembodiments, other fuels may be employed, e.g., other hydrocarbon fuels,pressurized or not. Where fuel source 26 is not pressurized, a pump orcompressor may be included to pressurize the fuel received from fuelsource 26. Fuel flow control valve 24 is configured to control theamount of fuel supplied to fuel delivery system 14, or moreparticularly, to reformer 34. In embodiments, where fuel source 26 isnot pressurized, fuel flow control valve 24 may include a pump orcompressor or may be a pump or compressor.

Merging chamber 32 is in fluid communication with the output ofcompressor 20 and fuel flow control valve 24, and is configured toreceive and combine the fuel and oxidant and discharge a feed mixturecontaining both the fuel and the oxidant. The oxygen to carbon molarratio (substantially the same as the volume ratio under anticipatedoperating conditions) supplied to reformer 34 may vary with the needs ofthe application, and may be, for example and without limitation, in therange of 0.5 to 2. The corresponding oxygen content of the oxidant maybe, for example and without limitation, 5% to 50% by molar ratio (e.g.,volume ratio). Reformer 34 is configured to receive the feed mixture andto reform the feed mixture into a reformed fuel having flammables,including primarily hydrogen (H₂) and carbon monoxide (CO), and methaneslip, e.g., 0.25%-3%, and trace amounts of higher hydrocarbon slip, suchas ethane. The total flammables content of the reformed fuel, associatedwith the corresponding ranges immediately above, may be, for example andwithout limitation, in the range from near 0% to approximately 80%. Invarious embodiments, other gases in various proportions may be includedin the reformed fuel in varying amounts, e.g., depending on theoxidant/fuel ratio of the feed stream supplied to reformer 34,including, for example and without limitation, nitrogen (N₂), carbondioxide (CO₂), also small amounts of steam. The form of merging chamber32 may vary with the needs of the application. For example, in one form,merging chamber 32 is a simple plumbing connection joining the oxidantstream with the fuel stream. In various embodiments, any arrangementthat is structured to combine an oxidant stream with a fuel stream, withor without mixing, may be employed. In some embodiments, a mixingchamber, e.g., having swirler vanes to mix the streams, may be employed,e.g., as part of merging chamber 32 or disposed downstream of mergingchamber 32.

Reformer 34 is in fluid communication with merging chamber 32, and isoperative to receive the fuel and oxidant from merging chamber 32. Inone form, reformer 34 is a catalytic reactor having a catalyst 36.Catalyst 36 may be any catalyst suitable for reforming a gaseoushydrocarbon fuel with an oxidant. Some suitable catalysts include, forexample and without limitation, an active material including group VIIInoble metals, such as Pd, Pt, Rh, Ir, Os and Ru. A carrier may beemployed in conjunction with the catalyst, e.g., a high surface areacarrier, including, for example and without limitation, stabilizedalumina, zirconia and/or silica-alumina. A catalyst support may also beemployed, for example and without limitation, pellets in a fixed bedarrangement, or a coated monolith or honey comb support, e.g., formed ofa metallic or refractory. One suitable refractory is cordierite. In aparticular form, reformer 34 is a catalytic partial oxidation (CPOX)reformer configured to reform the fuel with the oxidant using catalyst36. In other embodiments, other types of reformers may be employed.Combustion chamber 18 is in fluid communication with reformer 34.Disposed downstream of reformer 34 is a temperature sensor 38.Temperature sensor 38 is configured to sense the temperature of thereformed fuel after it exits reformer 34. A sense line 40 electricallycouples temperature sensor 38 to fuel flow control valve 24. In otherembodiments, sense line 40 may be an optical or wireless link. Fuel flowcontrol valve 24 is configured to control the amount of fuel supplied toreformer 34 based on the temperature of the gases, e.g., the reformedfuel, exiting the reformer 34.

In various embodiments, fuel delivery system 14 includes one or moreadditional components, which may include one or more of a cooler 42, ajunction 44, a check valve 46, a junction 48, a check valve 50, a valve52, a valve 54, a startup heating system 67 and one or more heaters 80.Cooler 42 is configured to reduce the temperature of the reformed fueloutput by reformer 34. In one form, cooler 42 is a heat exchanger thatis cooled by engine 12 coolant. In other embodiments, cooler 42 may bean air cooled heat exchanger, or may be one or more of other types ofcooling systems. In embodiments so equipped, combustion chamber 18 is influid communication with cooler 42, and is configured to receive thecooled reformed fuel from cooler 42.

Engine air intake 16 is in fluid communication with valve 52, which isin fluid communication with reformer 34 and cooler 42 via junction 44.In one form, valve 52 is a back-pressure regulating valve. In otherembodiments, valve 52 may be one or more of any type of valve. Junction44 is operative to allow the venting of some or all of the reformed fueldischarged by reformer 34 from combustion chamber 18 and direct thevented amount of the reformed fuel to another location via valve 52,such as to engine air intake 16, to an engine exhaust (not shown), toatmosphere, or to another venting location, including a device orapplication.

Valve 54 is in fluid communication with fuel supply 26 and junction 48.Junction 48 is in fluid communication with combustion chamber 18 viacheck valve 50. Valve 54 is configured to selectively provide unreformedfuel to combustion chamber 18. Check valve 46 is configured to preventthe backflow of unreformed fuel toward junction 44, hence preventing thebackflow of unreformed fuel toward reformer 34 and valve 52. Check valve50 is configured to prevent backflow from combustion chamber 18 intofuel delivery system 14.

Startup heating system 67 is in fluid communication with merge chamber32, and is configured to heat the feed mixture received from mergechamber 32 to a sufficient temperature to achieve catalyticauto-ignition of the fuel and oxidant upon its exposure to catalyst 36in reformer 34 in order to start up reformer 34. Startup heating system67 includes a start control valve 69 having a valve element 70 and avalve element 72; and a feed mixture heater 74. In one form, valveelements 70 and 72 are part of a combined valving element or system. Theinlets of valve elements 70 and 72 are downstream of and fluidly coupledto merging chamber 32. The outlet of valve element 70 is fluidly coupledto reformer 34 for providing the feed mixture to catalyst 36 of reformer34. The outlet of valve element 72 is fluidly coupled to the inlet offeed mixture heater 74. In one form, start control valve 69 is athree-way valve that operates valve elements 70 and 72 to direct flowentering valve 69 into catalytic reactor 34 directly from merge chamber32 and/or via feed mixture heater 74. It is alternatively consideredthat other valve arrangements may be employed, such as a pair ofindividual start control valves in place of start control valve 69 withvalve elements 70 and 72.

Feed mixture heater 74 includes a heating body 76 and a flow coil 78disposed adjacent to heating body 76. The outlet of feed mixture heater74 is fluidly coupled to reformer 34 for providing heated feed mixtureto catalyst 36. In the normal operating mode, valve elements 70 and 72direct all of the feed mixture directly to reformer 34. In the startupmode, feed mixture is directed through feed mixture heater 74 via flowcoil 78, which is then heated by heating body 76. In one form, all ofthe feed mixture is directed through feed mixture heater 74, although inother embodiments, lesser amounts may be heated, and some of the feedmixture may be passed directly to reformer 34 from merge chamber 32.

Feed mixture heater 74 is configured to “light” the catalyst 36 ofcatalytic reactor 34 (initiate the catalytic reaction of fuel andoxidant) by heating the feed mixture, which is supplied to catalyticreactor 34 from feed mixture heater 74. In one form, the feed mixture isheated by feed mixture heater 74 to a preheat temperature above thecatalytic auto-ignition temperature of the feed mixture (the catalyticauto-ignition temperature is the temperature at which reactions areinitiated over the catalyst, e.g., catalyst 36). Once catalyst 36 islit, the exothermic reactions taking place at catalyst 36 maintain thetemperature of catalytic reactor 34 at a controlled level, based on theamount of fuel and oxidant supplied to catalyst 36. Also, once catalyst36 is lit it may no longer be necessary to heat the feed mixture, inwhich case valve elements 70 and 72 are positioned to direct all of thefeed mixture directly to the catalytic reactor 34, bypassing feedmixture heater 74. In some embodiments, feed mixture heater 74 may bemaintained in the “on” position when engine 12 is not operating, but isrequired to start quickly.

Heaters 80 are disposed adjacent to catalytic reactor 34 and configuredto heat catalyst 36. In one form, heaters 80 are also configured tomaintain catalyst 36 at a preheat temperature that is at or above thecatalytic auto-ignition temperature for the feed mixture supplied toreactor 34. This preheat temperature may be maintained during times whenengine 12 is not operating, but is required to start quickly. Someembodiments may employ either or both of startup heating system 67 andheater(s) 80. In other embodiments, it is alternatively considered thatanother heater 82 may be used in place of or in addition to startupheating system and heater(s) 80, e.g., a heater 82 positioned adjacentto catalytic reactor 34 on the upstream side. Such an arrangement may beemployed to supply heat more directly to catalyst 36 in order toinitiate catalytic reaction of the feed mixture in an upstream portionof catalytic reactor 34.

In one form, heaters 74, 80 and 82 are electrical heaters, although itis alternatively considered that in other embodiments, indirect ordirect combustion heaters may be employed in addition to or in place ofelectrical heaters. Also, although the present embodiment employs bothfeed mixture heater 74 and heaters 80 to rapidly light the feed mixtureon the catalyst, it is alternatively considered that in otherembodiments, only one such heater may be employed, or a greater numberof heaters may be employed.

During operation, the oxidant, e.g., air, is pressurized by compressor20 and discharged therefrom toward merge chamber 32. Fuel is deliveredto merge point from fuel supply 26 via valve 24, which controls the rateof flow of the fuel. The oxidant and fuel combine at merge chamber 32,and are directed to reformer 34. During a start cycle of engine system10, heating body 76 is activated, and valve elements 70 and 72 areactivated by a control system (not shown) to direct fuel and oxidantthrough feed mixture heater 74. In various embodiments, some or all ofthe fuel and oxidant feed stream may be directed through feed mixtureheater 74. Heating body 76 adds heat to the feed stream to raise itstemperature to the catalytic auto-ignition temperature, i.e., atemperature sufficient for catalytic auto-ignition of the feed streamupon contact with catalyst 36. The catalytic auto-ignition temperaturemay vary with the type of catalyst used and the life of the catalyst.For example, with some catalysts, such as at least some of thosementioned herein, the catalytic auto-ignition temperature may be 300° C.at the start of the catalyst's life, but may be 450° C. near the end ofthe catalyst's life. In various embodiments, one or more of heaters 80and 82 may be employed to heat the catalyst and/or feed stream to atemperature sufficient for catalytic auto-ignition of the feed stream.

The fuel and oxidant are reformed in reformer 34 using catalyst 36.Temperature sensor 38 senses the temperature of the reformed fuelexiting reformer 36. The temperature data from temperature sensor 38 istransmitted to flow control valve 24 via sense line 40. Valve 24controls the flow of fuel, and hence the oxidant/fuel mixture based onthe sensed temperature, thus maintaining catalyst 36 at a desiredtemperature. The reformed fuel exiting reformer 34 is then cooled bycooler 42 and discharged into combustion chamber 18 via junctions 44 and48 and check valves 46 and 50.

In some circumstances, such as a cold start of engine system 10, it maybe desirable to start engine 12 by supplying unreformed fuel tocombustion chamber 18, and then transition from unreformed fuel toreformed fuel as reformer 34 reaches the ability to reform the fuel. Forexample, in some situations, fuel is supplied to combustion chamber fromfuel supply 26 via flow control valve 54. Reformer 34 may be startedbefore, during or after engine 12 is started, using one or more ofstartup heating system 67, and heater(s) 80 and 82, e.g., depending uponthe embodiment and the needs of the particular application, and theneeds of the particular start cycle, e.g., cold start vs. hot restart.Valves 24, 52 and 54 form a valve system that is configured totransition between 100% unreformed fuel and 0% reformed fuel beingsupplied to combustion chamber 18 and 0% unreformed fuel and 100%reformed fuel being supplied to the combustion chamber 18. When reformer34 is started, e.g., is capable of catalytic auto-ignition of the feedmixture, valves 24, 52 and 54, controlled by a control system (notshown), transition from supplying 100% of the fuel being delivered tocombustion chamber 18 in the form of unreformed fuel with 0% reformedfuel, to supplying 100% reformed fuel and 0% unreformed fuel tocombustion chamber 18. In one form, the transition is a gradualcontinuous process. In other embodiments, the transition may be a suddentransition or otherwise stepwise transition. In either case, during thetransition, in some embodiments, excess reformed fuel may be vented,e.g., to engine air intake 16, bypassing combustion chamber 18, e.g.,until the complete transition to 100% reformed fuel being supplied tothe combustion chamber is made. In other embodiments, valves 24, 52 and54 may modulate the flow of reformed and unreformed fuel withoutproducing an excess of reformed fuel during the start cycle. During thestart cycle, the output of compressor 20 may be varied in order tocontrol the rate of flow of oxidant before, during and after thetransition to supplying combustion chamber 18 with reformed fuel. Theoutput of compressor 20 may also be varied during normal engine 12operations in response to demand for reformed fuel.

In one form, during normal operations of engine 12, e.g., after engine12 has been started and has achieved steady state operation, combustionchamber 18 is supplied with 100% reformed fuel. In other embodiments, amixture of reformed fuel and unreformed fuel may be supplied tocombustion chamber 18.

In various embodiments, fuel delivery system 14 controls the output ofreformed fuel by varying the output of compressor 20 and by varying theamount of fuel delivered by valve 24 via a control system (not shown).In some embodiments, a valve (not shown) downstream of compressor 20 maybe employed to be able to respond more quickly to a demand for higher orlower flow. In some embodiments, the valve may vent excess flow at lowerengine 12 operating points, e.g., to intake 16, to atmosphere, or toengine 12 exhaust. In such embodiments, upon a demand for more outputfrom fuel delivery system 14, the valve may be closed in order to reduceor eliminate venting. Upon a demand for decreased output from fueldelivery system 14, the valve would increase the amount of ventedoxidant.

In some embodiments, it may be desirable for engine 12 to changeoperating points quickly, e.g., to switch from low power to high poweror from high power to low power fairly quickly. In the event theparticular engine 12 configuration is able to change operating pointsmore quickly than the particular fuel delivery system 14 maximumresponse rate, some embodiments of fuel delivery system 14 may beconfigured to produce an excess of reformed fuel at a particularoperating point or range of operating points in order to provideoperating margin. In such embodiments and situations, the excessreformed fuel may be vented, e.g., to air intake 16 via valve 52,bypassing combustion chamber 18. In such embodiments, valve 52, which isin fluid communication between reformer 34 and air intake 16, isconfigured to control the amount of flow of the reformed fuel tocombustion chamber 18 by bypassing a portion of the reformed fuel to airintake 16, thereby diverting that portion of reformed fuel flow fromcombustion chamber 18.

In some embodiments, valve 52 is configured to increase the ventedamount of the reformed fuel in response to a decrease in engine poweroutput; and is configured to decrease the vented amount of the reformedfuel in response to an increase in engine power output. Thus, forexample, if an increase in engine 12 output were commanded, the amountof flow of reformed fuel vented to air intake 16 would be reduced byvalve 52 under the direction of a control system (not shown), thusincreasing the amount of reformed fuel delivered to combustion chamber18. On the other hand, if a reduction in engine 12 output werecommanded, the amount of flow of reformed fuel vented to air intake 16would be increased by valve 52 under the direction of the controlsystem, thus decreasing the amount of reformed fuel delivered tocombustion chamber 18. Hence, the ratio of the portion of reformed fuelsupplied to combustion chamber 18 relative to the portion of reformedfuel supplied to air intake 16 may be changed so that fuel deliverysystem 14 may be able to respond more quickly to changes the operatingpoint (e.g., power output) of engine 12, and in some embodiments,without adversely affecting catalyst 36, for example, by otherwisecreating an off-design transient condition by attempting to followdemand for reformed fuel more quickly than fuel delivery system 14 canreadily respond. In some embodiments, by avoiding off-design transientconditions, the adverse effects of operation at off-design transientconditions on the life of catalyst 36 may be reduced or eliminated. Inaddition, in some embodiments, the ability to more quickly respond tochanging demand by controlling the venting of reformed fuel flow, e.g.,to air intake 16, may increase the ability of fuel delivery system 14 torespond to other changing conditions, such as a change in fuelcomposition, humidity or an engine or engine system component output.

In some embodiments, it may be desirable to limit the amount of reformedfuel provided to air intake 16, in which case fuel delivery system 14may be configured to supply no reformed fuel to air intake 16 at orabove a selected engine 12 operating point. In some embodiments, thismay be the maximum power operating point of engine, below which reformedfuel is provided via valve 52 to air intake 16, e.g., in proportion tothe output of engine 12, with greater amounts of reformed fuel beingprovided to air intake 16 at lower power points. In other embodiments,fuel delivery system 14 may be configured to supply no reformed fuel toair intake 16 at or above a other selected engine 12 operating points.In some embodiments, fuel delivery system may be configured to reduce orterminate the flow of reformed fuel to air intake 16, e.g., once stableengine operation has been achieved.

Embodiments of the present invention include a method for operating anengine, comprising: providing a combustion chamber of the engine with afuel; starting the engine using the fuel; starting a reformer, whereinthe reformer is configured to reform at least some of the fuel;transitioning from the provision of fuel to the combustion chamber to aprovision of reformed fuel; and providing only reformed fuel to thecombustion chamber.

In a refinement, the combustion chamber is a pre-combustion chamber.

In another refinement, the transitioning is performed after the reformerhas reached a catalytic auto-ignition temperature.

In yet another refinement, the engine is an internal combustion engine.

In a further refinement, the fuel is natural gas.

In a yet further refinement, the reformer is a catalytic partialoxidation (CPOX) reformer.

Embodiments of the present invention include a method for operating anengine, comprising: operating a reformer to reform a fuel; supplying afirst portion of the reformed fuel to a combustion chamber of the engineduring engine operation; venting a second portion of the reformed fuel;wherein the first portion and the second portion are supplied to therespective combustion chamber and venting location at a first ratio;changing an engine operating condition; and supplying the first portionand the second portion to the respective combustion chamber and ventinglocation at a second ratio in response to the change in the engineoperating condition.

In a refinement, the combustion chamber is a pre-combustion chamber.

In another refinement, the engine is an internal combustion engine.

In yet another refinement, the fuel is natural gas.

In still another refinement, no reformed fuel is supplied to the ventinglocation at or above a selected engine operating point.

In yet still another refinement, the selected engine operating point isa maximum power operating point.

In a further refinement, the reformer is a catalytic partial oxidation(CPOX) reformer.

Embodiments of the present in engine system, comprising: an engine; acompressor operative to pressurize an oxidant; a reformer in fluidcommunication with the compressor and a source of fuel, wherein thereformer is configured to receive the oxidant and fuel received from thesource of fuel, and to reform the fuel; a cooler in fluid communicationwith the reformer and configured to reduce the temperature of thereformed fuel output by the reformer; and a combustion chamber of theengine in fluid communication with the cooler, wherein the combustionchamber is configured to receive the cooled reformed fuel from thecooler.

In a refinement, the reformer is a catalytic partial oxidation (CPOX)reformer.

In another refinement, the combustion chamber is a pre-combustionchamber.

In yet another refinement, the engine is a piston engine.

In still another refinement, the engine system further comprises anengine air intake, wherein the compressor is configured to increase thepressure of the oxidant to above the pressure at the engine air intake.

In yet still another refinement, the engine system further comprises anengine air intake and a valve in fluid communication between thereformer and the air intake, wherein the valve is configured to controlan amount of flow of the reformed fuel to the combustion chamber byventing a portion of the reformed fuel to the air intake.

In a further refinement, the valve is configured to increase a ventedamount of the reformed fuel in response to a decrease in engine poweroutput; and wherein the valve is configured to decrease a vented amountof the reformed fuel in response to an increase in engine power output.

In a yet further refinement, the engine system further comprises a valveconfigured to control an amount of fuel supplied to the reformer.

In a still further refinement, the engine system further comprises atemperature sensor configured to sense the temperature of the reformedfuel exiting the reformer, wherein the valve is configured to controlthe amount of fuel supplied based on the temperature of the reformedfuel exiting the reformer.

In a yet still further refinement, the engine system further comprises avalve system configured to transition between 100% unreformed fuel and0% reformed fuel supplied to the combustion chamber and 0% unreformedfuel and 100% reformed fuel supplied to the combustion chamber.

In an additional further refinement, the reformer includes a catalyst,further comprising a heating system configured to heat the catalyst to acatalytic auto-ignition temperature prior to, during or after startup ofthe engine.

Embodiments of the present invention include an engine system,comprising: an engine; a reformer configured to receive an oxidant and afuel and to reform the fuel using the oxidant; a combustion chamber ofthe engine in fluid communication with the reformer, wherein reformedfuel is received into the combustion chamber; and a valve systemconfigured to transition between 100% unreformed fuel and 0% reformedfuel supplied to the combustion chamber and 0% unreformed fuel and 100%reformed fuel supplied to the combustion chamber.

Embodiments of the present invention include an engine system,comprising: an engine; a reformer configured to receive an oxidant and afuel and to reform the fuel using the oxidant; a combustion chamber ofthe engine in fluid communication with the reformer, wherein reformedfuel is received into the combustion chamber; an engine air intake; anda valve in fluid communication between the reformer and the air intake,wherein the valve is configured to control an amount of flow of thereformed fuel to the combustion chamber by venting a portion of thereformed fuel.

In a refinement, the valve is configured to increase a vented amount ofthe reformed fuel in response to a decrease in engine power output; andwherein the valve is configured to decrease a vented amount of thereformed fuel in response to an increase in engine power output.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment(s), but on the contrary, is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims, which scope is to be accordedthe broadest interpretation so as to encompass all such modificationsand equivalent structures as permitted under the law. Furthermore itshould be understood that while the use of the word preferable,preferably, or preferred in the description above indicates that featureso described may be more desirable, it nonetheless may not be necessaryand any embodiment lacking the same may be contemplated as within thescope of the invention, that scope being defined by the claims thatfollow. In reading the claims it is intended that when words such as“a,” “an,” “at least one” and “at least a portion” are used, there is nointention to limit the claim to only one item unless specifically statedto the contrary in the claim. Further, when the language “at least aportion” and/or “a portion” is used the item may include a portionand/or the entire item unless specifically stated to the contrary.

What is claimed is:
 1. A method for operating an engine, comprising:operating a reformer to reform a fuel; supplying a first portion of thereformed fuel to a combustion chamber of the engine during engineoperation; venting a second portion of the reformed fuel at a ventinglocation; wherein the first portion and the second portion are suppliedto the respective combustion chamber and venting location at a firstratio; changing an engine operating condition; and supplying the firstportion and the second portion to the respective combustion chamber andventing location at a second ratio in response to the change in theengine operating condition.
 2. The method of claim 1, wherein the engineis an internal combustion engine.
 3. The method of claim 1, wherein thefuel is natural gas.
 4. The method of claim 1, wherein no reformed fuelis supplied to the venting location at or above a selected engineoperating point.
 5. The method of claim 4, wherein the selected engineoperating point is a maximum power operating point.
 6. The method ofclaim 1, wherein the reformer is a catalytic partial oxidation (CPOX)reformer.
 7. An engine system, comprising: an engine; a reformerconfigured to receive an oxidant and a fuel and to reform the fuel usingthe oxidant; a combustion chamber of the engine in fluid communicationwith the reformer, wherein reformed fuel is received into the combustionchamber; and a valve system configured to transition between 100%unreformed fuel and 0% reformed fuel supplied to the combustion chamberand 0% unreformed fuel and 100% reformed fuel supplied to the combustionchamber, and the valve system including a valve in fluid communicationwith the reformer and a venting location, and being configured tocontrol a flow of the reformed fuel to the combustion chamber by ventinga portion of the reformed fuel at the venting location.
 8. An enginesystem, comprising: an engine; a reformer configured to receive anoxidant and a fuel and to reform the fuel using the oxidant; acombustion chamber of the engine in fluid communication with thereformer, wherein reformed fuel is received into the combustion chamber;an engine air intake; and a valve in fluid communication between thereformer and the air intake, wherein the valve is configured to controlan amount of flow of the reformed fuel to the combustion chamber byventing a portion of the reformed fuel.
 9. The engine system of claim 8,wherein the valve is configured to increase a vented amount of thereformed fuel in response to a decrease in engine power output; andwherein the valve is configured to decrease a vented amount of thereformed fuel in response to an increase in engine power output.